Tip: Be aware you have enabled at least one of the servers defined in the /etc/pacman.d/mirrorlist file. Otherwise all what you get is a misleading error message: error: no database for package: package-name.

To update a New Arch Linux base system after installation you may enter

# pacman -Sup --noconfirm > pkglist

Now open that textfile with an editor and delete all lines that are not URLs.
Next, bring that list with you to a place where you have internet and either download the listed packages manually or run wget in an empty directory:

# wget -nv -i ../pkglist

Tip: When using cygwin or some other kind of Windows environment to download the packages the filenames will get mangled, since default Windows file naming requires to escape e.g. colons. To avoid this (under cygwin, since it doesn't follow such restrictions) use wget --restrict-file-names=unix.

Take all the *.pkg.tar.gz files back home, put them in /var/cache/pacman/pkg and finally run

# pacman -S package-name

A simple example

This is a simple way to install a package you have downloaded:

# pacman -U /root/Download/packagename.tar.gz

This is how to install several packages you have installed into a directory

# pacman -U /root/Download/*.tar.gz

A slightly contrived example

Scenario: you have two Arch Linux machines, 'Al' (with internet connection) and 'Bob' (without internet connection), and you need to install some NVIDIA packages and their dependencies on 'Bob'. In this example, the wanted packages are nvidia, nvidia-utils, and xf86-video-nouveau, but you want to use a dedicated directory instead of /var/cache/pacman/pkg/ and a dedicated repository called nvidia (instead of the usual core, extra etc...)

Generate a list of packages to download

This can be done on any Arch Linux machine which has up-to-date repository data bases (see above for links to database files); to create the list of links to the required packages, use:

The file nvidia.list will contain links to the listed packages and any others which they depend on which are not already installed on 'Al'. Unless you have cleared your cache the packages you have installed will be in your cache location. You can check /etc/pacman.conf for the location. It is probably something like /var/cache/pacman/pkg/.

Download/copy the packages and their dependencies

Obviously this requires an internet connection, so on 'Al' create a directory called /path/to/nvidia for the files and run:

# wget -P /path/to/nvidia/ -i /path/to/nvidia.list

Then copy the dependencies you have already installed from the cache. Either find them manually by browsing https://www.archlinux.org/packages/ or if the total size of all your packages is not too large just copy them all

# cp /var/cache/pacman/pkg/* /path/to/nvidia/

Create a repository database just for these packages

This can be done on either 'Al' or 'Bob' using the repo-add command which comes with pacman (from version 3?); first, change to the /path/to/nvidia directory where the packages were downloaded, then create database file called nvidia.db.tar.gz:

$ cd /path/to/nvidia
# repo-add nvidia.db.tar.gz *.pkg.tar.xz

Transfer the packages

Now all the packages have been downloaded, you do not need 'Al' anymore. Copy the contents of /path/to/nvidia to a the temporary NVIDIA packages cache directory on 'Bob'. In this example, this folder is called /home/me/nvidia:

$ cp /path/to/nvidia/* /home/me/nvidia

Next, pacman must be made aware of this new repository of packages. First copy your current pacman.conf:

# cp /etc/pacman.conf /etc/pacman.conf.old

Now in /etc/pacman.conf make sure that your SigLevel is set to Never as your repository will not provide signatures

SigLevel = Never

and add the following lines at the bottom of pacman.conf:

[nvidia]
Server = file:///home/me/nvidia

You may also need to comment out the other repositories so stale defaults do not cause failed attempts to download from online
Now, instruct pacman to synchronize with the dedicated NVIDIA repository we created:

# pacman -Sy

This command finds the nvidia.db.tar.gz file in /home/me/nvidia and expands it to /var/lib/pacman/sync/nvidia to create a database of packages contained in the NVIDIA repository.

Install the packages

Finally install the packages:

# pacman -S nvidia nvidia-utils xf86-video nouveau

Restoring online sources

Should Bob ever be put online we can restore access to the online sources by replacing /etc/pacman.conf with the previously created /etc/pacman.conf.old.